Magnetron tuning cavity and waveguide coupler



Oct. 27, 1959 H. K. JENNY 2,910,620

MAGNETRON TUNING CAVITY AND WAVEGUIDE comma Filed Oct. 15, 1957 2 Fig. S n (I l2 J g I Z 33 q H 23 30 32 2 DIEL EC rA'lc 22 Fig. 3

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- k HANS KARL JENNY 0/ ATTORN EYS ted States Patent MAGNETRON TUNING CAVITY AND WAVEGUIDE COUPLER Hans Karl Jenny, Whippany, N.J., assignor, by mesne assignments, to the United States, of America as repre- This invention relates to a magnetron oscillator of the plural-anode cavity type and more particularly to an improved structural arrangement for coupling the tuning cavity and output waveguide with cavities of a magnetron for the transfer of oscillation energies.

A cavity type magnetron is, quite satisfactory as an oscillator for the generation of radio frequencies having associated wavelengths in the centimeter range. The generated wavelength from such types of magnetrons is dependent upon the physical size of each anode cavity, and for short wavelengths, the anode cavitiesmust be made correspondingly small.

One particularly useful form of such magnetron oscillator utilizes a central linear cathode with an anode structure comprising a group of cavity resonators disposed symmetrically about the central cathode. This type of magnetron is comparatively readily and inexpensively manufactured since the cavity resonators are formed by anode vanes which extend radially inward from an outer cylindrical wall, toward an axially disposed cathode. The cavities surrounding the cathode serve to fix the oscillation frequency of the magnetron and are determinative of the oscillation Wavelengths.

Since it is often necessary that a magnetron generate oscillations having wavelengths of one centimeter or less, it is apparent that the magnetron structural components must be quite small with the resultant difficulty in their assembly and fabrication. This becomes a particular problem since it is necessary to use small, compact vacuum-tight seals between the cavity resonators and the tuning cavity and also with the waveguide.

Accordingly, it is the broad object of this invention to provide a common and effective coupling arrangement for the transfer of oscillation energies from selected magnetron cavity resonators to the tuning cavity and waveguide.

Another object is to provide such a unitary coupling device which is further arranged to prevent intercommunication of oscillation energies between the waveguide and tuning cavity.

Briefly, this invention accomplishes these and other objects by utilizing a coupling member in the form of a panel which is constructed of mica, ceramic, glass or a synthetic material having equivalent low dielectric properties. The panel is disposed between independent conduits which are in communication with selected cavity resonators and connects the conduits with the waveguide and also the tuning cavity of the magnetron. In addition, a choke device in the form of three intercommunicating tubes is positioned between the waveguide and the tuning cavity of the magnetron and functions to prevent intermingling or transfer of oscillation energies between the tuning cavity and waveguide.

For a better understanding of the invention, reference may be had to the accompanying drawing, wherein:

Fig. l is a transverse sectional view of the invention, applied to one type of magnetron and associated tuning cavity and waveguide structure;

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Fig. 2 is a slightly enlarged view taken along line 2-2 of Fig. 1;

Fig. 3 is an enlarged view of a portion of Fig. 2; and 4 is a view taken generally on the line4-4 of Referring now to Fig. 1, there is shown a magnetron comprising a shell S of cylindrical shape enclosed within a housing H and having a cathode 10 positioned axially therein. A plurality of anode vanes 11 extend radially inwardly from the inner periphery of the shell S and have their inner edges 12 disposed in spaced relation with the cathode 10. The anode vanes :11 are in effect partitions forming open end compartments 13 which function as a group of cavity resonators disposed generally symmetrically about the cathode 10.

The tuning structure for the magnetron includes a conduit 20 of rectangular shape as shown, which communicates at one end with a selected cavity resonator 13 and has its other end communicating through. a wall 21. A tuningcavity 22, is mounted adjacent the other face of the wall 21 and in general alignment with the conduit 20. All of the resonators 13 are in communication by way of a central space 23 about the cathode 10 and consequently all of the cavity resonator frequencies will be controlled by the tuning cavity 22. The tuning cavity 22 is provided with a plunger 24 having an operating arm 25 for adjusting the reactance of the tuning cavity 22 as desired. A second cavity resonator is similarly arranged as shown to communicate with a waveguide 26 by means of a second conduit 27 of rectangular shape which also communicates through the wall 21.

A panel 30 of low dielectric material such as glass, mica, or ceramic, is mounted in abutting relation or surface contact with the outer face of wall 21 and the material ofwhich the panel 30 is constructed has the property of transmitting oscillation energies from the cavity resonators 13 and the conduits 20 and 27 to the tuning cavity 22 and waveguide 26 and in eifect provides a common coupling unit between the conduit 20 and the tuning cavity 22 and also between the conduit 27 and the waveguide 26. 7

One end of each of conduits 20 and 27 is fitted in the shell S in sealed relation therewith while the other ends of the conduits are positioned to abut one face of the panel 30 and are preferably maintained in sealed relation with the one face of the panel as is shown in detail in Fig. 3. Similarly, the inner ends of the tuning cavity and the waveguide will be, as shown, disposed in abutting relationship with the other face of the panel 30- and preferably in sealed relationship therewith.

A choke means in the form of a T connection is shown in enlarged detail in Figs. 3 and 4 and comprises three communication tubular sections 31, 32, and 33 which are disposed between and provide communication between the tuning cavity 22 and waveguide 26. The open end of section or leg 31 is in communication with the cavity 22 while the open end of section 32 is in communication with the waveguide 26. The section 33 extends laterally from sections 31 and 32 and has a closed end while the walls 35 of sections 31 and 132 are slotted and have their edges positioned in abutting relation with the other face of panel 30 providing communication between the panel and the choke means and preventing energies from passing between the tuning cavity 22 and waveguide 26.

The choke sections 31, 32, and 33 will be designed to be quarter wavelength of the oscillations in the cavity resonators 13 and the wavelength of the oscillations may be tuned by the tuning cavity plunger 24 as desired. The choke sections 31, 32, and 33 will offer infinite impedance, to any oscillations which may try to pass between '2 I a tuning cavity 22 and waveguide 26* The section 33 has a closed end, as shown, which is remote from panel 30 and since the panel 30 communicates with both sections 31 and 32, the oscillation energies will not pass betweenthe tuning cavity and waveguide.

'While there has been described a preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein within the scope of the invention, which is to be limited only by the appended claims.

What is claimed is:

1. A plural-anode cavity type magnetron having a shell and radial vanes extending inwardly therefrom providing a plurality of communicating oscillatory cavity resonators, a housing enclosing said shell, a panel of di' electric material disposed in surface contacting relation with one wall of said housing, a tuning cavity with a tuning plunger therein and having an open end abutting the outer face of said panel and a closed end, an output Waveguide spaced from said tuning cavity and having one open end abutting said outer face of the panel and its other open end extending outwardly therefrom to supply magnetron oscillations to an external consumption device, choke means interconnecting said tuning cavity and said waveguide, a first energy transmitting conduit having one end in communication with one of said cavity resonators and its other end communicating through said one wall of .the housing to be in abutting relation with the inner face of said panel and aligned with said tuning cavity, a second energy transmitting conduit having one end in communication with another cavity resonator and its other end communicating through said one wall of the housing to be in abutting relation with the inner face of the panel and aligned with said waveguide, said panel being effective to transmit oscillation energy from all of said communicating cavity resonators to both the tuning cavity and the waveguide and said choke means being efiective to prevent the transfer of oscillation energy therebetween.

2. A plural-anode cavity type magnetron having a shell and radial vanes extending inwardly therefrom 4 providing a plurality of communicating oscillatory cavity resonators, a housing enclosing said shell, a panel of dielectric material disposed in surface contacting relation with one wall of said housing, a tuning cavity with a tuning plunger therein and having an open end abutting the outer face of said panel and a closed end, an output waveguide spaced from said tuning cavity and having one open end abutting said outer face of the panel and its other open end extending outwardly therefrom to supply magnetron oscillations to an external consumption device, choke means comprising an open end conduit providing communication between said tuning cavity and said waveguide and having a slotted area abutting the outer face of said panel, a first energy transmitting conduit having one end in communication with one of said cavity resonators and its other end communicating through said one wall of the housing to be in abutting relation with the inner face of said panel and aligned with said tuning cavity, a second energy transmitting conduit References Cited in the file of this patent UNITED STATES PATENTS 2,501,545

Sproull Mar. 21, 1950 2,624,864 Herlin et a1. Jan. 6, 1953 2,639,404 Everhart et al. May 19, 1953 2,658,165 Evans et a1. Nov. 3, 1953 2,659,029 Clogston et a1. Nov. 10, 1953 2,724,090 Moore Nov. 15, 1955 2,769,937 Hutchinson et a1. Nov. 6, 1956 2,782,383 Olive Feb. 19, 1957 

